System and method for delivering encrypted information in a communication network using location identity and key tables

ABSTRACT

Access to digital data is controlled by encrypting the data in such a manner that it can be decrypted only at a specified location, within a specific time frame, and with a secret key. Data encrypted in such a manner is said to be geo-encrypted. This geo-encryption process comprises a method in which plaintext data is first encrypted using a data encrypting key that is generated at the time of encryption. The data encrypting key is then encrypted (or locked) using a key encrypting key and information derived from the location of the intended receiver. The encrypted data encrypting key is then transmitted to the receiver along with the ciphertext data. The receiver both must be at the correct location and must have a copy of the corresponding key decrypting key in order to derive the location information and decrypt the data encrypting key.

RELATED APPLICATION DATA

This is a continuation-in-part of co-pending patent application Ser. No.09/699,832, filed Oct. 30, 2000, for SYSTEM AND METHOD FOR USINGLOCATION IDENTITY TO CONTROL ACCESS TO DIGITAL INFORMATION, andco-pending patent application Ser. No. 09/758,637, filed Jan. 10, 2001,for CRYPTOGRAPHIC SYSTEM AND METHOD FOR GEOLOCKING AND SECURING DIGITALINFORMATION.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to controlling access to digital datathrough a communication network based on location. More particularly,the present invention relates to a method and apparatus for encryptingdigital data in a communication network in such a manner that it can bedecrypted only at a specified location and using a secret key.

2. Description of Related Art

Rapid advances in computer, telecommunications and networking technologyhave enabled new opportunities and applications that were impossiblejust a few years ago. These advances are exemplified by the rapid growthof network systems seeking to delivery “high-value” content securely toauthorized recipients. Examples of such networks include those thathandle confidential, sensitive, or classified information in the healthcare, financial, and national security fields. They also includenetworks that handle intellectual property or copyrighted data such ascomputer software, literary works, and entertainment products.Controlling the security of information in such systems, includingconfidentiality, authenticity, integrity, authorized use, transactionsecrecy, site protection, etc., has proven to be a difficult problemthat has reduced the benefit that businesses and consumers mightotherwise enjoy from such systems.

One technology that is critical to protecting information on thesenetworks is cryptography. Cryptography is the use of codes and ciphersto protect data from unintended disclosure or modification. It isprimarily used to control access to communications transmitted over opennetworks, but may also be used to control access to stored data. In atransmission utilizing cryptography to protect digital data, the senderconverts the original data, or “plaintext,” into a coded equivalentcalled “ciphertext” using an encryption algorithm. The ciphertext isthen decoded (or decrypted) by the receiver and thereby turned back intoplaintext. The encryption algorithm uses a key, which in digital systemsis a string of bits. In general, the larger the number of bits in thekey, the longer it takes to break the code using so-called “brute force”methods.

Keys form the basis of all cryptographic systems. Two separatecryptographic key methods have been widely adopted by users ofelectronic networks: private-key cryptography and public-keycryptography. With private-key cryptography (also known as symmetriccryptography), the sender and receiver use a common secret key toencrypt and decrypt data. With public-key cryptography (also known asasymmetric cryptography), the sender and receiver use different butmathematically related keys to encrypt and decrypt the data. Inparticular, the sender encrypts the data using a public key that isunique to the receiver, while the receiver decrypts the data using thecorresponding private key that is known only to the receiver. Becauseseparate keys are used, public-key cryptography also can be used toprovide digital signatures for authentication and non-repudiation. Inthis case, the sender signs the data using the sender's private key,while the receiver validates the data using the sender's public key.

Owing to their different mathematics, private-key cryptography isgenerally much more efficient than public-key cryptography. It runsfaster and can provide comparable security using shorter keys.Consequently, most network systems use private-key cryptography toencrypt and decrypt most types of data. Public-key cryptography, if usedat all, is presently used only to distribute the secret keys used withprivate-key cryptography and to digitally sign data.

The shared secret keys used with private-key cryptography can bedistributed using either private-key or public-key methods. Private-keydistribution methods are particularly well suited to broadcast andmulticast applications where a central, shared server transmits data toone or more receivers simultaneously, such as subscription television,and to other applications that involve communications to or from acentral server. Public-key distribution methods are particularly wellsuited to applications involving communications between two entitiesthat do not trust each other and do not employ a shared server, such aselectronic mail delivered across the Internet and connections betweenweb browsers and web servers.

With both public-key and private-key cryptography, anyone knowing thesecret key needed to decrypt the data can decrypt and access that data,assuming the method of encryption is known (which is generally assumed).It does not matter where the person is located or how the personacquired the data. For some applications, however, it would be desirableto control access to data based not only on a secret key, but also onlocation. For example, in the context of digital cinema, such acapability would enable a producer of digital movies to be assured thatits products could only be decrypted in certain theaters whose locationswould be known in advance. Or, a provider of entertainment products suchas movies and subscription television would be assured that its productscould only be decrypted within the premises of its customers or within aparticular geographic region. This capability would guard against manythreats, including the unauthorized distribution of copyright-protectedworks over the Internet or through other means. Even if the keys werecompromised, recipients would not be at the proper location to enabledecryption. The related patent applications referenced above disclose amethod and system for encrypting digital data based on location.

It would also be desirable to have a capability to control access todata based on the distribution path of the data. For example, such acapability would enable a provider of protected works to be assured thatits works were distributed through specific channels. Persons acquiringthe product through other channels would then be unable to decrypt thedata, even if they acquired the secret key. This capability could beused even when location is not a factor for authorizing decryption.Location-based encryption and path-dependent encryption wouldsignificantly enhance the security of data.

Another limitation of conventional encryption systems, particularlythose that are based entirely on private-key cryptography, is that keymanagement is vested with a single entity. Key management refers to thecontrol over distribution of keys within a network. By restricting keymanagement to a single entity, data providers that do not have keymanagement authority are limited in their ability to control access totheir digital data through the networks. Therefore, in addition to usinglocation-based encryption and path-dependent encryption, it would bedesirable to provide a method and system whereby multiple data providerscan independently manage the secret keys they use to communicate withother providers and receivers.

SUMMARY OF THE INVENTION

In accordance with the present invention, access to digital data iscontrolled by encrypting the data in such a manner that, in a singledigital data acquisition step, it can be decrypted only at a specifiedlocation and with a secret key. If the sender so elects, access todigital data also can be controlled by encrypting it in such manner thatit must traverse a specific route from the sender to the recipient inorder to enable decryption of the data.

Data encrypted in such a manner is said to be geo-encrypted. Thisgeo-encryption process comprises a method in which plaintext data isfirst encrypted using a random data encryption key that is generated atthe time of encryption. The data encrypting key is then encrypted (orlocked) using a location value and a key encrypting key. The encrypteddata encrypting key is then transmitted to the receiver along with theciphertext data. The receiver both must be at the correct location andmust have a copy of a corresponding key decrypting key in order toderive the location key and decrypt the data encrypting key. After thedata encrypting key is decrypted (or unlocked), it is used to decryptthe ciphertext. If an attempt is made to decrypt the data encrypting keyat an incorrect location or using an incorrect key decryption key, thedecryption will fail. In addition, the encrypted data encrypting key orciphertext optionally may be rendered unusable so that it becomesimpossible to ever decrypt that particular ciphertext. The dataencrypting key may also be encrypted in a manner that it can only beaccessed at a certain time or during a specific time frame.

In accordance with an embodiment of the invention, the ciphertext datacan be routed through one or more intermediary distributors before beingtransmitted to a final receiver. One method for doing this involvesencrypting the data encrypting key with a location value and keyencrypting key for the distributor. The distributor then decrypts thedata encrypting key and re-encrypts it using a location value and keyencrypting key for the receiver. The distributor does not have todecrypt the ciphertext, although nothing would prevent it from doing so.Another method for routing the ciphertext through a distributor involvesencrypting the data encrypting key first with a location value and keyencrypting key for the final receiver and then with a location value andkey encrypting key for the distributor. The distributor removes itslayer of encryption from the key before forwarding it to the receiver.If there are multiple distributors, the data encrypting key issuccessively encrypted with a location value and key encrypting key foreach distributor on the path, but in reverse order. As the encrypted keyis passed from one distributor to the next, each distributor removes itslayer of encryption. With this method, none of the distributors candecrypt the data encrypting key because it remains encrypted with thelocation value and key encrypting key for the final receiver. Thus, thedistributors cannot access the plaintext. This method also forces theciphertext to follow a particular path to the receiver.

Another embodiment of the invention provides a method for distributingshared secret keys, specifically shared key encrypting/decrypting keys.These secret keys are transmitted from one place to another using thesame techniques as for distributing any form of digital data.Specifically, a secret key that is to be distributed to a receiver isencrypted using a data encrypting key. The data encrypting key, in turn,is encrypted using a location value and an existing key encryptingassociated with the receiver. The transmission is also digitally signedto ensure that only the owners of keys can create, change, and deletetheir keys. The sender can manage the secret keys required fordecryption in a secure manner that is transparent to the recipient. As aconsequence of its ability to manipulate the secret keys, the sender ofencrypted data retains the ability to control access to its plaintexteven after its initial transmission.

The aforementioned methods of the present invention employ a combinationof private-key (i.e., symmetric) and public-key (i.e., asymmetric)cryptography. Plaintext data is encrypted and decrypted with private-keycryptography. The random data encryption key, however, can be encryptedand decrypted using either private-key cryptography or public-keycryptography. If private-key cryptography is used, the key encryptingkey and key decrypting key are identical. The key encrypting/decryptingkey is also kept secret. In contrast, if public-key cryptography isused, the key encrypting key is a separate public key, while the keydecrypting key is a mathematically-related but distinct private key.Only the private, key decrypting key needs to be kept secret. Public-keycryptography is also used for authentication of the communications usedto distribute the secret key encrypting/decrypting keys used withprivate-key cryptography. Public-key cryptography may also be used toauthenticate other communications. It should be understood thatprivate-key cryptography, public-key cryptography, or both could be usedto distribute key decrypting keys in accordance with alternativeembodiments of the invention.

In one embodiment of the invention, a communication network includes aproducer device, a distributor device, a receiver device, and anadministrator device. Each of these devices includes a key table thatstores a plurality of key encrypting and key decrypting keys, and publicand private signature keys. Some of these keys may be used withprivate-key cryptography, while others are used with public-keycryptography. The producer device encrypts the source digital data, suchas a television episode or motion picture. The distributor deviceenables the secure transmission of the digital data initiated by theproducer to either other distributors or to a designated receiver. Thereceiver device provides for receipt and end-user access to theplaintext of the digital data.

The administrator device has administrative control over some or all ofthe keys in the key tables. Providers, including producers, distributorsand administrators, can add new keys to their own devices and to thedevices of others, although they may be limited in the total number ofkeys that can be added to any particular device. Providers also canchange and delete any key they own in any device. In addition, each userof the present invention may own one or more keys in the key table oftheir own device to handle their specific needs. Further, individualelectronic devices within the communications network may incorporate anycombination of producer, distributor, receiver and administratorfunctionality within a single unit so that a single node may embodywhatever functionality is deemed appropriate.

In summary, the geo-encryption methods of the present invention extendthe conventional methods of encryption to location-based and path-basedencryption. If encrypted data is acquired at an unauthorized location orfrom an unauthorized channel through interception, transmission, ordownloading, it cannot be decrypted because the location informationpertaining to this unauthorized location would be inconsistent with theencrypted data. Further, if a device containing ciphertext is moved to anew, unauthorized location, it will not be possible to decrypt theciphertext even if the device has the correct keys. It should beunderstood, however, that data could be securely moved between locationsby authorized persons by re-encrypting or re-locking the random dataencryption key for the new location. In order to compromise thegeo-encryption, an adversary would have to know the encryption methods,location, and secret keys. Security ultimately depends on keeping thekeys secret, since the methods and location may become known.

It should be appreciated that geo-encryption can be used even whenlocation is not to be a factor in granting access. In that case, theencryption is made for a universal location that includes the entireworld. This permits decryption anywhere in the world provided thereceiver has the key decrypting key needed to decrypt the random dataencrypting key. It also should be appreciated that geo-encryption can beused when time is not to be factor in granting access, therebypermitting decryption over an indefinite period of time.

A more complete understanding of the system and method for deliveringencrypted information in a communication network using location identityand key tables will be afforded to those skilled in the art, as well asa realization of additional advantages and objects thereof, by aconsideration of the following detailed description of the preferredembodiment. Reference will be made to the appended sheets of drawings,which will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating access to digital informationdetermined by location identity in accordance with an embodiment of thepresent invention;

FIG. 2 is a block diagram illustrating components of a location identityattribute;

FIG. 3 is a block diagram illustrating components of a location value ofthe location identity attribute;

FIG. 4A is a block diagram illustrating an embodiment of acommunications network in accordance with the invention;

FIG. 4B is a block diagram illustrating an exemplary key table;

FIG. 5 is a flowchart illustrating a method for geo-encrypting digitalinformation using a location identity attribute;

FIG. 6 is a flowchart illustrating a method for accessing geo-encrypteddigital information using the location identity attribute;

FIG. 7 is a diagram illustrating the operation of exemplary Geo-Encryptand Geo-Decrypt functions;

FIG. 8 is a diagram illustrating the operation of exemplary Geo-Lock Keyand Geo-Unlock Key functions;

FIG. 9 is a diagram illustrating the operation of an exemplaryGeo-Relock Key function;

FIG. 10 is a diagram illustrating the operation of an exemplaryGeo-Relay Encrypt function; and

FIG. 11 is a diagram illustrating the operation of an exemplary ExportKey and Import New Key functions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention satisfies the need to control the secureinterchange of digital data so as to prevent unauthorized access to thedata. More specifically, the present invention provides methods andapparatus for encrypting digital data in such a manner that it can bedecrypted only at a specified location within a specified time frame andwith a secret key. In the detailed description that follows, likeelement numerals are used to describe like elements illustrated in oneor more of the figures. Various terms are used throughout the detaileddescription, including the following:

Administrator Device. A form of provider device (defined below) utilizedby administrators of the keys stored in other devices.

Associating Location Identity. A method of marking digital dataencryption keys with a location identity attribute.

Coordinate System. Location will be designated by latitude and longitudewhich is a coordinate system based on degrees that uniquely identifiesany location on the Earth. Latitude is measured as an angle from theequator of the Earth (0 degrees) to the North Pole (90 degrees North) orto the South Pole (90 degrees South). Circles that run parallel to theplane of the equator form lines of latitude. All whole number latitudelines are equidistant from each other. A location's latitude is ameasure of the angle between the plane of the equator and linesprojected from the center of the Earth. Longitude lines are made bygreat circles that intersect with both the North and South Poles. Eachlongitude can be thought of as dividing the Earth in half. Longitudesare measured in half circles of 0 degrees to 180 degrees East and from 0degrees to 180 degrees West from the Royal Greenwich Observatory inGreenwich, England. The 0 degree longitude line is also referred to asthe prime meridian. A location's longitude is a measure of the anglebetween the plane made by its great circle and the prime meridian.

Distributor Device. A type of provider device (defined below) utilizedby distributors of digital data.

Enforcing Location Identity. A method of providing or denying access todigital information through its associated location identity attribute.

Geocode. A unique coding of a location on earth usually associated witha coordinate system. Some geocodes identify a point location, such aswhen a place is identified by its latitude and longitude. Other geocodesmay identify a region such as a zip code.

Geo-encrypt. An enforced association between a geographic area definedby a location identity attribute and digital data where access isgranted to users within an area defined by the location identityattribute who also hold a secret key.

Geo-encrypted Data. Digital data containing encryption keys that havebeen associated with a location identity attribute, and that can only beaccessed within an area defined by the location identity attribute usinga secret key.

Location. A geographic place including, but not limited to, a precisepoint location, an area or region location, a point location includedwithin a proximate area, or combinations of places on earth. Locationcan also include height (or altitude) to identify position above orbelow the surface of the earth, or time to identify position in atemporal dimension.

Location Identity. A precise coding of a location including, but notlimited to, an attribute of information to precisely define the locationat which the information is to be accessed. Location identity may be acoding of a point location, a region, a region with an associated pointlocation, a corridor (i.e., center line with length on either side ofthe center line), or by any other precise identification of a locationin space and time.

Location Variance. The minimum resolution at which a geocode of alocation may fail to exactly distinguish it from adjacent locations.

Playback Location. The location portion of the location identityattribute at which access to digital information will be allowed.

Player Location. The location of a receiver device attempting to playback a geolocked file.

Producer Device. A form of provider device (defined below) utilized byproducers of digital data.

Provider Device. Electronic devices, systems, networks, and the likewith the minimum capacity to geo-encrypt and transmit digital data.

Proximity. A zone or area that includes the location.

Receiver Device. Electronic devices, systems, networks, and the likewith the minimum capacity to receive and geo-decrypt digital data andkeys, and to acquire location information. These electronic devices willoften include a processing capability to execute program instructionsand a memory capacity for short-term and long-term data storage, and mayfurther include the ability to transmit information.

Universal Location. Any geographic place on earth.

The foregoing definitions are not intended to limit the scope of thepresent invention, but rather are intended to clarify terms that areused in describing the present invention. It should be appreciated thatthe defined terms may also have other meanings to persons havingordinary skill in the art. These and other terms are used in thedetailed description below.

Referring now to FIG. 1, a schematic illustration of the presentinvention depicts how access to digital data is determined by locationidentity. As defined above, location identity refers to an attribute ofinformation that precisely determines the geographic area or region inwhich the information is accessible. Two geographic areas denoted by Aand B are shown on a map 101 within the continental United States.Information 130 is represented in digital format, and has an associatedlocation identity attribute 131 that precisely defines the geographicarea A as the region in which the digital information can be accessed.If a receiver device 112 is located within the geographic region A, thenthe digital information 130 will be accessible by the receiver device.Conversely, if a receiver device 122 is located within the geographicregion B (or anywhere else besides geographic region A), then thedigital information 130 will not be accessible. Location identity thusrepresents an attribute of digital information that determines theprecise geographic region within which the information can be accessed.Digital data having location-based encryption keys are termed“geo-encrypted” and systems that enforce location identity geolock theassociated digital data to the geographic region defined by the locationidentity attribute.

FIG. 2 depicts a location identity attribute 140 as comprising two itemsof information: (a) a location value 142, and (b) a proximity value 143.The location value 142 corresponds to the unique geographic position ofa particular place. Many different coordinate systems, such as latitudeand longitude, have been developed that provide unique numericalidentification of any location on earth. For the purposes of thisinvention, any coordinate system that uniquely identifies a place can beused for the location value 142 of the location identity attribute 140.The proximity value 143 corresponds to the extent of a zone or area thatencompasses the location. The location identity attribute 140 maycomprise a point location or an exact location if the proximity value143 is set to zero, null, empty, etc., or some other value indicatingthat the area referred to by the location identity attribute is a uniquepoint location. It should be appreciated that the proximity value 143 isdifferent from location variance. The proximity value 143 refers to arepresentation of an area or region, whereas location variance is theminimum resolution at which a geocode or a location may fail to exactlydistinguish it from an adjacent location.

FIG. 3 depicts the location value 142 in greater detail. As noted above,there are numerous different coordinate systems in common use thatprovide a set of numbers that uniquely identify every location withinthe coordinate system. In the present invention, the location value 142is defined in terms of a unique location designation or geocode as shownat 142 a. Latitude 144 and longitude 145 using a conventional coordinatesystem may then further define the geocode. Other known systems, such asthe Earth Centered, Earth Fixed Cartesian coordinate system, UniversalTransverse Mercator (UTM), Military Grid Reference System (MGRS), WorldGeographic Reference System (GEOREF) etc., could also be advantageouslyutilized. In addition to latitude 144 and longitude 145, the locationvalue could further include an altitude 146 as shown at 142 b, whichcorresponds to the height of the location above sea level.Alternatively, the location value could further include a time value 147as shown at 142 c that may be defined in terms of a date and/or timerange. This allows the definition of location identity to consider bothgeographic and/or temporal access to information.

Any geographic region or area that contains the location value 142 ofthe location identity can serve as the proximity value 143 for thelocation identity attribute 140. The proximity value 143 may comprise arectangular region defined by two adjacent longitude lines (providinghorizontal edges) and two adjacent latitude lines (providing verticaledges). Alternatively, the proximity value 143 may comprise a circularregion represented by a single number defining the radius around thelocation. The circular region can be further defined as an ellipticalarea either centered at the location, or a circular or elliptical areathat contains the location but not necessarily as the centroid. Inanother alternative, the proximity value 143 may comprise an irregularclosed polygon, or a corridor. In yet another alternative, the proximityvalue 143 may correspond to a known geographic region, such as thecountry of Brazil. Other types of known geographic regions that candefine the proximity value 143 can include postal zip codes, states,counties, incorporated cities, etc.

Referring now to FIG. 4A, a block diagram illustrating an embodiment ofa communications network employing methods and apparatus according tothe invention. The communications network includes one or more producerdevices 300, one or more receiver devices 400, and one or moreadministrator devices 310 that are coupled together via a network 200(e.g., a wide area network such as the Internet). The producer devices300 each denote a communication system utilized by a producer of digitaldata, such as a video production facility. The receiver devices 400 eachdenote a communications system utilized by an end user, such as atelevision set-top-box. The administrator devices 310 each denote acommunication system utilized by an administrator of the communicationnetwork. As illustrated, producer devices 300, administrator devices310, and receiver devices 400 are each respectively comprised ofapplications processors 302, 312, 402 and memory units 304, 314, 404. Itshould be appreciated that there may be a plurality of producer devices300, administrator devices 310, and receiver devices 400 within thecommunication network, and that the network would also be functionalwith just a single device in any one of the categories.

The communications network may be configured with the producer devices300 in direct communication with the receiver devices 400.Alternatively, one or more distributor devices 320 may also be connectedto the aforementioned communications network interposed between theproducer devices 300 and the receiver devices 400. In this alternativeconfiguration, information communicated from the producer devices 300 tothe receiver devices 400 passes through the distributor devices 320. Asillustrated, distributor devices 320 are each comprised of anapplications processor 322 and a memory unit 324. In the descriptionthat follows, the term “provider device” is used to collectively referto producer devices 300, administrator devices 310, and distributordevices 320 unless specified otherwise. Moreover, the manner in whichthe producer devices 300, receiver devices 400, administrative devices310 and distributor devices 310 communicate is not critical to theinvention, and any form of communication network having some or all ofthese components could be advantageously utilized. Further,communications from provider devices may be point-to-point to specificreceiver devices or multicast to plural receiver devices simultaneously.

The producer devices 300, administrator devices 310, distributor devices320 and receiver devices 400 also include respective GPS receivers 309,319, 329, 409 coupled to respective applications processors 302, 312,322, 402. Specifically, it is anticipated that each of the devices hasaccess to GPS signals and the respective GPS receivers can process thosesignals to produce location information, including latitude, longitude,altitude, and time, although all of these values may not be used. Thereceiver devices 400 (and in some cases the distributor devices 320) usethe location information processed by the GPS receivers 409 to determinelocation identity information (discussed below). The other devices usethe GPS receivers to seed the generation of random numbers used in theencryption process (also described below). It should be appreciated thatother methods of determining location identity information and/orgenerating random numbers could also be advantageously utilized as wellknown in the art.

The respective memory units 304, 314, 324, and 404, of the producerdevices 300, administrator devices 310, distributor devices 320, andreceiver devices 400 may further comprise volatile and/or non-volatilememory components sufficient to store data, including informationcontent, software instructions, and encryption keys. In a preferredembodiment of the invention, the memory units 304, 314, 324, and 404 arefurther organized to include key tables 306, 316, 326, and 406 thatallow for the storage of a plurality of keys that are used withprivate-key and public-key cryptography. These keys are used by eachdevice 300, 310, 320, and 400 together with location information toencrypt and decrypt random data encryption keys and to sign and validatemessages. The use and distribution of the keys within the key tables isan important aspect of the invention that will be described in greaterdetail below.

It should be appreciated that any of the producer devices 300,administrator devices 310, distributor devices 320, and/or receiverdevices 400 can be implemented in hardware or software. The preferredembodiment is a tamperproof hardware device that would protect both thesecrecy of keys and the integrity of the functions performed by thedevices; however, the functions themselves do not have to be keptsecret. The devices further may be included in larger systems or devicesthat handle the communications and perform other application-relatedfunctions and auditing functions. Auditing functions might log the useof the device and, possibly, transmit that information to a designatedauditing entity.

For example, in one embodiment, a receiver device 400 might be includedin a set-top-box (STB) used by video service providers to receivebroadcast entertainment content (e.g., television shows, movies, andother video programming). Whenever a program is decrypted, an auditrecord could be returned to the provider of the program. The STB wouldhave the capability to show a decrypted program on the monitor, but notto save or transmit the plaintext. In another embodiment, a receiverdevice 400 might be built into the equipment used at a movie theater.The equipment might have the capability to show a decrypted program andstore the content for a limited period of time, but not to transmit theplaintext. A provider device 300, 310, 320 might be built into acomputer system or such other equipment that is used to create, process,and transmit data.

In accordance with an embodiment of the present invention, the providerdevices 300, 310, 320 need to know the location of the receiver devices400 (or other ones of the provider devices). The provider devices 300,310, 320 may query the receiver devices 400 upon connection to thecommunication network, which then report back the location informationderived from GPS signals (or other method) to the provider devices.Alternatively, in the foregoing example, the video service providers mayalready know the location of the set-top-boxes since they correspond tothe physical address of customers of the video service providers. Eachset-top-box may further include a unique serial number that the providerdevices 300, 310, 320 can use to identify the receiver devices 400.

In a preferred embodiment, the key tables 306, 316, 326, 406 contain thekeys that each respective device uses to encrypt or decrypt random dataencryption keys and to sign or validate messages. As shown in FIG. 4B,an exemplary key table 306 contains a plurality of key records 307 ₁-307_(N). The key records 307 (also referred to herein simply as “keys”)each include a unique key identification (ID) that further comprises anOwner Identification (ID) code and a key name. The key records 307further include the associated key value (illustrated as KEY 1 throughKEY N). Every key in the table has an owner that is determined by thecorresponding Owner ID. The key name simply gives the name of the keywhile the key value gives the actual string of bits comprising the key.It should be understood that the key records 307 might also containother information, including the type of key and encryption method usedwith that key. For example, the key record 307 could specify whether thekey is to be used with private-key cryptography or public-keycryptography, and, if the latter, whether the key is a public-keyencrypting key, private-key decrypting key, private signature key, orpublic signature validation key. The key records 307 might also containan expiration date. The key records 307 for the public and private keysused with public-key cryptography might include digital certificates forthe keys. Some of this additional information may be part of the keyidentification. The other key tables 316, 326, 406 will have generallysimilar construction.

For example, the keys used by a television producer (e.g., AOL-TimeWarner, Inc.) to protect the data it produces for television viewingcould have key IDs with an owner ID uniquely identifying this particulartelevision producer as well as a plurality of key names, each of whichuniquely identifies a particular channel or network owned by thetelevision producer (e.g., HBO®, TNT®, TBS®, CARTOON NETWORK®, CNN®,CINEMAX®, etc.). Similarly, another television producer (e.g., The WaltDisney Co.) could have key IDs with an owner ID unique to thisparticular television producer along with key names corresponding toparticular channels or networks owned by this other television producer(e.g., Disney Channel®, ESPN®, ABC®, etc.).

In an embodiment of the invention, administrators will own at least onekey in the key table of every device. It should be appreciated thatthese keys could be unique to individual devices or common amongmultiple devices. One of these keys might be common to all devices,allowing any provider device 300, 310, 320 to transmit encrypted data toany receiver device 400. In addition, a provider of geo-encrypted datamay own one or more keys in the key tables of devices that are allowedto receive and decrypt data from that provider. In another embodiment,each device 300, 310, 320, 400 might own its own public-private keypair. The public key of the exemplary device could be given to anyprovider device, allowing the provider device to transmit encrypted datato the exemplary device without the need for a common key. It should beappreciated that many possible arrangements of keys are possible.

The keys in the key table are used to protect the transmission of dataencryption keys. Specifically, they are used with location informationto encrypt and decrypt the data encryption key and to sign and validatedata. It should be appreciated that secret keys in the key tables 306,316, 326, 406 would remain within the associated device while in use andwould never leave the device in unencrypted form. The key table could beorganized in any way, for example, as a sequential or linked list,binary search tree, or hash table. It also could be implemented as adatabase or other type of data repository. Secret keys cannot beexported from the device in the clear, but they can be exported inencrypted form. Operations for adding, changing, and deleting keysto/from a key table will be described later. It should be appreciatedthat in any given device keys could be distributed over multiple keytables or not even stored in a table per se. Accordingly, the key tablesdescribed herein are intended to denote the entire collection of keyswithin a device in any manner in which they are stored, maintainedand/or organized.

In a preferred embodiment, digital data is geo-encrypted using a set offunctions embedded within a provider device 300, 310, 320. Thisgeo-encrypted data is then transmitted to one or more receiver devices400 where it is decrypted using a set of functions embedded within thereceiver device 400. The transmission can be point-to-point, broadcastor multicast. The geo-encrypted data has a location identity attribute140 associated therewith so that subsequent access of the digitalinformation is limited to the geographic area specified by the locationidentity attribute 140. FIG. 5 illustrates a general method forassociating digital information with the location identity attribute 140that precisely defines the region in which access or playback of thedigital information will be allowed. In the present invention, thismethod would be performed either via a producer device 300, anadministrator device 310 or a distributor device 320.

More particularly, the method starts at step 500 with a command togeo-encrypt digital information using a location identity attribute. Afirst part of the method provides for the generation of the locationidentity attribute. At step 502, a playback location value 142 for thedigital information is retrieved and stored for later use. The playbacklocation value 142 is not the geographical location at which the methodis performed by the provider device 300, 310, 320, but rathercorresponds to the geographical location for a receiver device 400 atwhich access to the digital information will be allowed. At step 504, aproximity value 143 of the location identity attribute of the receiverdevice 400 is retrieved and stored for later use. Various methods forgenerating the location and proximity values 142, 143 will be describedin greater detail below. In addition to such methods, the location andproximity values 142, 143 may also be pre-stored and retrieved frommemory, or the end user may be queried to provide the information. Atstep 506, the playback location and proximity values 142, 143 are usedto generate the location identity attribute 140.

A second part of the method provides for the generation of encryptionkeys and the encryption of the plaintext digital information. At step508, a key ID 505 is used to select and retrieve a key encrypting key307 a from the key table of the corresponding provider device 300, 310,320. The location identity 140 is then used at step 510 to derive alocation value 507 and a shape parameter 509. The shape parameter 509defines a shape of an area of interest without identifying the specificlocation corresponding to the area of interest. The shape parameter 509is a locationless translation of the proximity portion of the locationidentity attribute 140. Locationless refers to the characteristic of theshape parameter 509 as defining the shape of a proximate area withoutreference to any actual location. As will be further described below,the receiver device 400 uses the shape parameter 509 to fully determinethe location value needed for recovering the location key.

Then, at step 514, the process generates a random data encrypting key524.

This data encrypting key 524 is used to encrypt the plaintext digitalinformation 518 at step 516 to produce geo-encrypted digital information520. The data encrypting key 524 is then encrypted at step 522 using thelocation value 507 and the key encrypting key 307 a. The geo-encrypteddigital information 520, the encrypted data encrypting key 526 (alsoreferred to below as a cipher key), the shape parameter 509, and the keyID 505 are then communicated to the receiver device 400. Attempts todecrypt the geo-encrypted information 520 by a receiver device 400 willbe denied unless the location of the receiver device 400 matches thelocation specified by the location identity attribute 140 and thereceiver device 400 has the correct key decrypting key identified by thekey ID 505.

FIG. 6 shows a general method for enforcing access to geo-encrypteddigital information by location. Software or embedded firmwareinstructions operating in association with the applications processor402 of the receiver device 400 would cause the method to be performed.Particularly, the method starts at step 600 with a command to decryptthe geo-encrypted digital information 520. A first part of the methodprovides for the generation of the location value 507. At step 602, themethod determines the location of the receiver device. It should beappreciated that numerous ways to determine the receiver device locationare possible and are described in the aforementioned co-pending patentapplications commonly owned by the applicant. In a preferred embodiment,the GPS receiver 409 within or coupled to the receiver device 400provides this location information 604. The device location information604 is then used in conjunction with the shape parameter 509 receivedfrom the provider of the geo-encrypted digital information to generatethe location value 507 at step 606. As will be appreciated, the locationvalue 507 generated by the receiver device must match the location value507 used by the provider device to geo-encrypt the digital information,otherwise the receiver device 400 will be unable to geo-decrypt theencrypted digital information 520.

In a second part of the method, the location value 507 is used with akey decrypting key 307 b to geo-decrypt the encrypted digitalinformation. The key decrypting key 307 b is retrieved from the keytable of the receiver device at step 608 in accordance with the key ID505 received from the provider device. It should be appreciated that thekey decrypting key 307 b retrieved at step 608 must correspond to thekey encrypting key 307 a used in geo-encrypting the digital information;otherwise, the geo-decryption will fail. At step 612, the selected keydecrypting key 307 b and the generated location value 507 are used todecrypt the data encrypting key 526. If the location of the receiverdevice is consistent with the location value 507 used by the providerdevice, the decryption will recover the original data encrypting key524. Lastly, the data encrypting key 524 is used to decrypt thegeo-encrypted digital information 520 to recover the plaintext digitalinformation 518 at step 614.

Table 1 provided below lists an exemplary set of functions used in anembodiment of the present invention. It should be appreciated that thesefunctions can be incorporated into one or more of the aforementionedproducer devices 300, administrator devices 310, distributor devices320, and receiver devices 400. For each such function, Table 1 lists thevalues used as inputs (i.e., parameters) to the function and thecorresponding values produced as outputs (i.e., results) of thefunction. It should be appreciated that all functions using cryptographyin Table 1 use location information in some way. It should be furtherappreciated that these functions do not necessarily have to beimplemented as separate procedures or distinct program units of anytype, and could instead be combined or split into multiple units. Itshould also be noted that the inputs and outputs shown in Table 1 arenot necessarily external to a device and may instead be passed from onefunction to another within a single device. All of the functionsdescribed herein could further include error checking and handling, andit is anticipated that conventional methods for performing thesefunctions be utilized. A brief description of each function listed inTable 1 is provided with greater detail within the text below.

TABLE 1 Basic Functions Function Inputs/Parameters Outputs/ResultsDescription Geo-Encrypt Location ID, Shape Parm, Encrypt data and lockthe Key ID, Cipher Key, data encryption key using a Plaintext IV,Ciphertext location-derived secret key Geo-Decrypt Shape Parm, PlaintextDecrypt data after unlocking Key ID, the key Cipher Key, IV, CiphertextGeo-Lock Key Location ID, Shape Parm, Lock data encryption key Key ID,Cipher Key with location-derived secret Data Encrypting Key keyGeo-Unlock Key Shape Parm, Data Encrypting Unlock data encryption keyKey ID, Key with location-derived secret Cipher Key key Geo-Relock KeyShape Parm In, Shape Parm Out, Unlock data encryption key Key ID In,Cipher Key Out with one location-derived Cipher Key In, secret key andlock it with Location ID Out, another Key ID Out Geo-Relay Encrypt n,Shape Parm [j] Encrypt data and lock the Location ID [j]  for j to 1 ton, data encryption key with  for j from 1 to n, Cipher Key, multiplelocks that must be Key ID [j] IV, unlocked by successive relay  for jfrom 1 to n, Ciphertext stations before the data can Plaintext bedecrypted Create Key Key ID Create and add secret key to Replace Key KeyTable, replace key with Delete Key new value, or delete key Export KeyKey ID, Shape Parm, Geo-encrypt a key record in Location ID, Cipher Key,the Key Table so that it can Export Key ID IV, Cipher Key be securelyexported to Record, Signature another Key Table Import New Key ShapeParm, Add, change, or delete a key Import Export Key ID, record in theKey Table by Replacement Key Cipher Key, importing a geo-encryptedImport Deletion IV, key record and performing Key Cipher Key Record, theoperation only if signed Provider ID, by the owner or by an Signatureadministrator

As described above, the provider devices 300, 310, 320 include a keytable 306, 316, 326 and a private key 308, 318, 328, respectively, andmay receive a GPS signal as an input used to derive location informationfor decryption and to generate random values. The provider devices areadapted to execute a first set of functions, including Geo-Encrypt,Geo-Lock Key, Geo-Unlock Key, Geo-Relay Encrypt, and Geo-Relock Key. Theprovider devices may also be adapted to execute a second set offunctions, including Create Key, Replace Key, Delete Key, Export Key,Import New Key, Import Replacement Key, and Import Deletion Key. Thefirst set of functions are used to manage the encryption and decryptionof information using the keys contained in the key table, and the secondset of functions are used to manage the various key values in the keytables. In a preferred embodiment of the invention, the provider devices300, 310, 320 include all of the functions identified in Table 1, theoperation of which will be discussed in greater detail below.

The receiver devices 400 also include a key table 406 and receive a GPSsignal as input. In a preferred embodiment, the receiver devices 400contain only functions needed to decrypt geo-encrypted data and receivekeys. In particular, receiver devices 400 are adapted to execute theGeo-Decrypt and Geo-Unlock functions. The receiver devices may also beadapted to execute the Import New Key, Import Replacement Key, andImport Deletion Key functions. These functions enable users to receiveand decrypt geo-encrypted data and keys, but not to geo-encrypt data orkeys. The operation of these functions will also be discussed in greaterdetail below.

It should be appreciated that other combinations of functions arepossible. For example, a distributor device 320 could be given somewhatdifferent functionality from that of a producer device 300. Or, a singleprovider device 300, 310, 320 might be used by all entities thatproduce, distribute, and/or receive geo-encrypted data. If receiverdevices 400 are to have the capability to geo-encrypt their own filesand share them with other users, then they would likely need most, ifnot all, of the functionality of a provider device 300, 310, 320,including the capability to own their own keys and share keys with otherdevices. It should also be appreciated that the devices may includefunctions that are not described herein. They may have additionalfunctions to manage the key tables, for example, to limit the number ofkeys that an owner can include in a key table or to allow an owner todetermine which of its keys are included in a key table. The devices mayfurther include functions providing additional capabilities associatedwith digital rights management.

The operation of the Geo-Encrypt and Geo-Decrypt functions 700, 720 areillustrated in FIG. 7 with reference to Table 1. The Geo-Encryptfunction 700 has three inputs, including: (1) Location Identity (Loc ID)140; (2) Key ID 505; and (3) Plaintext 518. The Geo-Encrypt function 700encrypts the Plaintext 518 according to the location identified byLocation ID 140 in such a manner that the data can be decrypted only bya device that both is at that location and has the secret key identifiedby the Key ID 505. As a result, the Geo-Encrypt function 700 yields fouroutputs, including: (1) Shape Parameter (Shape Parm) 509; (2) Cipher Key526; (3) Initialization Value (IV) 708; and (4) Ciphertext 520. TheGeo-Encrypt function 700 includes as sub-functions pseudo-random numbergenerator (PRNG) 704 and Encrypt 706, and also accesses the Geo-Lock Keyfunction 800 (described below with respect to FIG. 8).

More particularly, the Geo-Encrypt function 700 generates a DataEncrypting Key 524 using the PRNG sub-function 704. In a preferredembodiment, the PRNG sub-function 704 is provided with raw GPS signaldata 707 in addition to other non-deterministic information (e.g.,determined by the state of the device). Assuming an initialization value(IV) is to be used, the PRNG sub-function 704 also generates a random IV708. The Encrypt sub-function 706 then encrypts the Plaintext 518 usingboth the Data Encrypting Key 524 and the IV 708 to produce a Ciphertextoutput 520. The Data Encrypting Key 524 is locked (i.e., encrypted)using the Geo-Lock Key function 800, using a location value derived fromthe location identified by the Location ID 140 and from the keyencrypting key identified by the Key ID 505. The Geo-Lock Key function800 provides as outputs Shape Parameter 509 and Cipher Key 526.

In a preferred embodiment, the Encrypt sub-function 706 comprises astrong encryption method, such as the Advanced Encryption Standard(AES), which has a block size of 128 bits and uses keys of size 128,192, and 256 bits. It should be appreciated that any other method ofencryption can also be used. The particular mode of encryption woulddepend on the algorithm, length of the Plaintext 518, and theapplication. Normally, when the Plaintext 518 is longer than a block ortwo, a mode such as output feedback, cipher feedback, or cipher blockchaining is used. In that case, the encryption process uses theinitialization vector (IV) 708 to initialize the encryption process. Ina preferred embodiment, the IV 708 is transmitted to the receiver device400 in order to initialize the decryption process. It should be noted,however, that the IV 708 does not have to be encrypted.

The Geo-Decrypt function 720 has five inputs, including: (1) Shape Parm509; (2) Key ID 505; (3) Cipher Key 526; (4) IV 708; and (5) Ciphertext520. The Geo-Decrypt function 720 decrypts Ciphertext 520 using DataEncrypting Key 524 and IV 708, and includes sub-function Decrypt 724 andaccesses the Geo-Unlock Key function 820 (described below with respectto FIG. 8). Data Encrypting Key 524 is determined by unlocking theCipher Key using the Geo-Unlock Key function 820. The Geo-Unlock Keyfunction 820 decrypts the Cipher Key 526 using the key decrypting keyidentified by Key ID and a location value determined from the Shape Parm509 and a GPS signal 727 in order to yield the Data Encrypting Key 524.The Decrypt sub-function 724 decrypts the Ciphertext 520 using the DataEncrypting Key 524 and IV 708 in order to reconstruct the Plaintext 518.It should be appreciated that the Decrypt sub-function 724 would be theinverse of the Encrypt sub-function 706 used by the Geo-Encrypt function700 described above.

In an embodiment of the invention, the Geo-Decrypt function 720 goesfurther and tests whether the recovered Plaintext 518 is authentic. Forexample, this procedure may be done using a message authentication code(MAC) that would be computed by the Geo-Encrypt function 700 as afunction of the Plaintext 518 and included with the data. It should beunderstood that any known method of computing a MAC could be used. Afterdecrypting the Ciphertext 520, the Geo-Decrypt function 720 would thencompute a MAC for the recovered Plaintext 518 If the MAC matches thatcomputed by the Geo-Encrypt function 700 and included with the data,then it can be assumed that the data was correctly decrypted. Thisimplies that the Geo-Decrypt function 720 was performed at the correctlocation and that it used the correct key decrypting key. If the MACdoes not match, then the Geo-Decrypt function 720 could output anindicator to this effect. Alternatively, the Geo-Decrypt function 720could take action that would henceforth render the data undecipherable.For example, the Geo-Decrypt function 720 could nullify the Cipher Key526 by replacing it with all zeros. With this additional capability, theGeo-Decrypt function 720 can ensure that, if an attempt is made todecrypt data at an incorrect location or using an incorrect keydecrypting key, any further attempts to decrypt the data will fail.

FIG. 8 illustrates the operation of the Geo-Lock Key and Geo-Unlock Keyfunctions 800, 820 with reference to Table 1. The Geo-Lock Key function800 is used to encrypt the Data Encrypting Key 524 so that it can besecurely distributed to a receiver device 400. The Geo-Lock Key function800 has three inputs, including: (1) Location ID (Loc ID) 140; (2) KeyID 505; and (3) Data Encrypting Key 524. The Geo-Lock Key function 800further includes a Mapping Encrypt (Mapping Enc) sub-function 802, a GetKey sub-function 806, and a Key Encrypt sub-function 812. The Geo-LockKey function generates two outputs, including: (1) Cipher Key 526; and(2) Shape Parm 509.

The Mapping Encrypt sub-function 802 converts the Location ID 140 into aLocation Value (Loc Val) 507 and the Shape Parm 509. In a preferredembodiment, the Mapping Encrypt sub-function 802 comprises a mappingfunction such as that described in co-pending patent application Ser.No. 09/758,637 commonly owned by the applicant, incorporated byreference herein. Particularly, the mapping function is used to mapdifferent coordinates within a proximate area into the same values. Themapping function is as follows:

f(x)=Δ*int(x/Δ)

where int is a function that returns the integer part of its argument inparentheses. Using x as the latitude of the geocode location and A asthe length of the side between the bounding latitudes; or x as thelongitude of the geocode location and A as the length of the sidebetween the bounding longitudes, a grid may be constructed over theentire latitude/longitude coordinate system. Every geocode within a gridcell will be transformed into the same value when the above function isapplied to its latitude and longitude. Since the “great rectangle”boundaries may not fall directly on boundaries that are exact multiplesof the length of the bounding sides, a locationless offset measure iscalculated using the lower bounding side and is used to linearly shiftthe grid. It should be appreciated that other methods for computingLocation Value 507 and Shape Parm 509 may also be employed within thescope and spirit of the present invention.

The Get Key sub-function 806 uses the Key ID 505 to retrieve theappropriate key encrypting key 307 a from a key table 306. Then, the KeyEncrypt sub-function 812 encrypts the Data Encrypting Key 524 using theLocation Value 507 and the key encrypting key 307 a. In a preferredembodiment, the Key Encrypt sub-function 812 first takes theexclusive-OR of the Data Encrypting Key 524 and the Location Value 507,and then encrypts the result using the key encrypting key 307 a. Theencryption would be implemented with a strong encryption method such asthe AES if private-key encryption is being used or RSA if public-keyencryption is being used, although it should be appreciated that otherencryption methods could be used. In an alternative embodiment, the KeyEncrypt sub-function 812 first encrypts the Location Value 507 with thekey encrypting key 307 a and then uses the result of that to encrypt theData Encrypting Key 524. With this embodiment, the Key Encryptsub-function 812 must use private-key cryptography.

It should be appreciated that the Geo-Lock Key function 800 can be usedto encrypt any key, not just the Data Encrypting Key 524 used to encryptthe Plaintext data. For example, the Geo-Lock Key function 800 can beused to place an additional lock on an already encrypted key. Thus, theData Encrypting Key 524 used by the Geo-Lock Key function 800 (andGeo-Unlock Key function 820) should be understood to refer to any key,whether already encrypted or not.

The Geo-Unlock Key function 820 is used to recover the Data EncryptingKey 524 from the Cipher Key 526. The Geo-Unlock Key function 820 hasthree inputs, including: (1) Shape Parm 509; (2) Key ID 505; and (3)Cipher Key 526. The Geo-Unlock Key function 820 further includes aMapping Decrypt (Mapping Dec) sub-function 822, a GPS Signal Processingsub-function 826, a Get Key sub-function 832, and a Key Decryptsub-function 836. The Geo-Unlock Key function 820 generates a singleoutput, i.e., Data Encrypting Key 524.

The GPS Signal Processing sub-function 826 receives a GPS signal 727 andprocesses the signal to determine the location of the receiver device400 in terms of GPS coordinate data 824. The Mapping Decryptsub-function 822 uses the GPS data 824 along with the Shape Parm 509 todetermine the Location Value 507. As described above, the MappingDecrypt sub-function 822 employs a mapping function such as thatdescribed in co-pending patent application Ser. No. 09/758,637. Itshould be appreciated that different methods for computing LocationValue 507 could also be used. The Get Key sub-function 832 operatessubstantially the same as the Get Key sub-function 806 described above.Particularly, the Get Key sub-function 832 uses the Key ID 505 toretrieve the appropriate key decrypting key 307 b from a key table 406of the receiver device 400. The Key Decrypt sub-function 836 decryptsthe Cipher Key 526 using the Location Value 507 and the key decryptingkey 307 b to recover the Data Encrypting Key 524. It should be notedthat the Key Decrypt sub-function 836 is substantially the inverse ofthe Key Encrypt sub-function 812 described above. In a preferredembodiment, the Key Decrypt sub-function 836 first decrypts the CipherKey 526 using the key decrypting key 307 b. This is performed usingeither private-key or public-key cryptography, depending on which wasused by the Key Encrypt sub-function 812. The Key Decrypt sub-function836 then takes the exclusive-OR of the result with the Location Value507 to recover the Data Encrypting Key 524. In an alternativeembodiment, the Key Decrypt sub-function 836 first encrypts the LocationValue 507 with the key decrypting key 307 b, and then uses the result todecrypt the Cipher Key 526 and recover the Data Encrypting Key 524. Inthis case, private-key cryptography is used for all steps, so the keydecrypting key 307 b is the same as the key encrypting key 307 a. If thereceiver device 400 does not have access to GPS signals either becauseit is not GPS-enabled or for some other reason, it should be appreciatedthat Location Value 507 may be set to a universal location. As a result,this will allow data intended for all locations to be decrypted from anylocation, but not other data.

When encrypted data (i.e., Ciphertext 520) is transmitted to a receiverdevice 400, it is transmitted along with a Cipher Key 526. The CipherKey 526 contains the Data Encrypting Key 524 enciphered in alocation-dependent manner. In a preferred embodiment, re-encryptionwould then involve deciphering (i.e., unlocking) the Data Encrypting Key524 and re-enciphering (i.e., locking it with a different locationvalue). It should be appreciated that the Ciphertext 520 itself is notdecrypted and re-encrypted. Relay encryption is similar, except that theCipher Key 526 is not initially unlocked. Instead, one or moreadditional locks are placed on top of the Cipher Key 526. Thus, theoriginal key may be nested under several layers of encryption, all ofwhich have to be removed in order to restore the original key. Thespecific functions used to perform these tasks are described in greaterdetail below.

FIG. 9 illustrates the operation of the Geo-Relock Key function 900 withreference to Table 1. The Geo-Relock Key function 900 receives fiveinputs, including: (1) Shape Parm In 902; (2) Key ID In 904; (3) CipherKey In 906; (4) Location ID Out 908; and (5) Key ID Out 910. TheGeo-Relock Key function 900 also receives a GPS signal 920. TheGeo-Relock Key function 900 produces two outputs, including: (1) ShapeParm Out 912; and (2) Cipher Key Out 914. The Geo-Relock Key function900 accesses the Geo-Unlock Key function 820 (described above) and theGeo-Lock Key function 800 (described above). The Geo-Unlock Key function820 decrypts the Cipher Key In 906 using Shape Parm In 902 and Key ID In904 in order to recover the Data Encrypting Key 524. Then, the Geo-LockKey function 800 re-encrypts Data Encrypting Key 524 using the newlocation value as determined by Location ID Out 908 and Key ID Out 910.It should be noted that the values for Key ID In and Key ID Out could bethe same or different depending on whether a new key encrypting key 307a is to be used in the process. Similarly, the location values could bethe same or different, depending on whether decryption is to take placeat the same or different location.

FIG. 10 illustrates the operation of the Geo-Relay Encrypt function 1000with reference to Table 1. The Geo-Relay Encrypt function 1000 hasinputs n 1002, Location ID [j] 1004 j, Key ID [j] 1006 j, Location ID[n] 1004 n, Key Id [n] 1006 n, and Plaintext 518. The input n 1002corresponds to the total number of sites the data is to pass through onits way to a final receiver (i.e., the nth site) and j is the set of allintegers from 1 to n−1. Thus, for every one of the 1 through n−1receiver sites, there is a corresponding Location ID [j] and Key ID [j],and for the nth receiver site there is a Location ID [n] and Key ID [n].As a result, the Geo-Relay Encrypt function 1000 will output Shape Parm[j] 1010 j (namely, Shape Parm [1], Shape Parm [2], . . . Shape Parm[n−1]), Shape Parm [n] 1010 n, Cipher Key 1008, IV 1012, and Ciphertext520. The Geo-Relay Encrypt function 1000 accesses the Geo-Encryptfunction 700 (described above with respect to FIG. 7) and the Geo-LockKey function 800 (described above with respect to FIG. 8). The Geo-LockKey function 800 is embedded in a loop so that it is executed n−1 times,as will be further described below.

The Geo-Relay Encrypt function 1000 accesses the Geo-Encrypt function700 to encrypt the Plaintext 518 and yield Ciphertext 520 substantiallyas described above with respect to FIG. 7. The Data encrypting keygenerated as part of that process is locked using the Geo-Lock Keyfunction 800 with inputs Location ID [n] 1004 n and Key ID [n] 1006 n toyield Cipher Key 1008, Shape Parm [n] 1010 n, and IV 1012. The CipherKey 1008 is then used as the Data encrypting key input in a loop inwhich the Geo-Lock Key function 800 is executed n−1 times. The loopbegins at step 1020 by initializing a counter by setting j equal to n−1.At step 1022, the counter is tested to determine whether j<1, i.e., acondition indicating that the end of the loop has been reached. If theend condition is met, the Geo-Relay Encrypt function 1000 is terminated.Conversely, if the end condition has not been met, the Geo-Lock Keyfunction 800 is accessed with inputs Location ID [j] 1004 j and Key ID[j] 1006 j to yield a new Cipher Key 1008 and Shape Parm [j] 1010 j. Thecounter j is then decremented at step 1024, and the loop returns to step1022 whereupon the end condition for the loop is again tested and theGeo-Lock Key function 800 again accessed if the end condition is notmet. With each decrement of the counter, another layer of encryption isadded to the Cipher Key 1008. When the end condition for the loop isfinally met, and the Geo-Relay Encrypt function 1000 terminated, thefinal Cipher Key 1008 is passed with the n−1 values of Shape Parm [j]1010 j, Shape Parm [n] 1010 n, Ciphertext 520, and IV 708 to the firstrelay station (e.g., distributor device). The first relay station willuse the Geo-Unlock Key function 820 with Shape Parm [1] and Key ID [1]to remove the first layer of encryption from Cipher Key 1008, the nextstation will use Shape Parm [2] and Key ID [2] to remove the secondlayer of encryption from Cipher Key 1008, and so forth. Finally, the endrelay station will produce the final Cipher Key after performing itsunlock. Assuming the final Cipher Key has been properly passed throughall relay stations and in the pre-determined order, the Ciphertext 520can be decrypted.

A preferred embodiment of the invention also includes a set of functionsfor managing secret key encrypting/decrypting keys in the key tableswhen the keys are used with private-key cryptography. The functionsprovide for the creation, replacement, deletion, and distribution of thekeys, using geo-encryption and geo-decryption for the distribution. Itshould be appreciated that the keys themselves can be distributed usingeither private-key cryptography or public-key cryptography with thegeo-encryption and geo-decryption functions. It should also beappreciated that somewhat different functions are needed to manage thepublic and private keys used with public-key cryptography, in particularany public-key encrypting keys, private-key decrypting keys, privatesignature keys, and public signature validation keys. A preferredembodiment of this invention uses existing methods to manage these keys,using the key table for storage of the keys. It should be furtherappreciated that if public-key cryptography is used exclusively for keymanagement, then the functions described herein to manage keys forprivate-key cryptography would not be required. It should also beappreciated that a combination of public-key and private-keycryptography could be used for key management.

Turning now to the management of secret key encrypting/decrypting keysused with private-key cryptography, every key in the key table of aproducer device 300, administrator device 310, distributor device 320,or receiver device 400 is owned by a particular provider. The providercan be a producer, distributor, administrator or any other entity thatprovides encrypted data. It should be appreciated that administratorsare special providers having administrative control over keys. It shouldbe further appreciated that each user of the present invention mayfurther own one or more keys in a given key table to handle theirspecific needs. In an embodiment of the invention, a key owned by aparticular provider is stored in the key table of the provider's device300, 310, 320 so that the provider can use it to encrypt data or keys.Providers can add new keys to their own devices 300, 310, 320 and to thedevices of others, although they may be limited in the total number ofkeys that can be added to any particular device. Providers also canchange and delete any key they own in any device.

When a new provider is added to the network, the administrator device310 will create one or more keys for the provider that can be used witheach device that could receive encrypted data from that provider. Someof these keys may be unique to the devices and will be owned by theprovider. The keys will be loaded into the key tables of the producerdevices 300, administrator device 310, distributor devices 320, and/orreceiver devices 400 that are to receive encrypted data from thatprovider. The keys will be transmitted remotely to the devices if thedevices are already in use in the field. In one embodiment of theinvention, the administrator device 310 can change and delete any key inthe key table of any other device even if it does not own the key. Inanother embodiment, the administrator device 310 cannot change or deletekeys that it does not own. It should be appreciated that if public-keycryptography is used for key management, it is not necessary for theadministrator device 310 to create and distribute keys on behalf of theprovider as described above. Instead, a provider can communicate withany other device using the public key of that device.

The functions described below support management of the secret keyencrypting/decrypting keys in key tables as shown in Table 1. Aspreviously noted, these keys are used with private-key cryptography, butmay be distributed using either public-key or private-key cryptography.In particular, the functions Create Key, Replace Key, and Delete Key areused to manage a provider's own secret keys in its own device. An ExportKey function is used to obtain a Key Record from the provider's keytable and geo-encrypt it so that the secret key can be securely exportedfrom the provider device 300, 310, 320 and transmitted to anotherdevice. Finally, the functions Import New Key, Import Replacement Key,and Import Deletion Key are used in remote devices to handle the importof a previously exported key from another device and update itscorresponding key table. In a preferred embodiment of the invention,public-key cryptography is used to authenticate the entity requesting achange in the key table of another device. This ensures that providerscan only add, change, and delete keys that they own. The preferredembodiment uses a strong public-key signature algorithm for thispurpose, such as RSA or DSA with keys of 2,048 bits or more.

As listed in Table 1, the Create Key function is used to create a newkey that is added to a key table. The Create Key function receives as aninput a Key ID. The PRNG sub-function may be used to generate a randomKey Value. Then, a Key Record is created using the Key Id and therandomly generated Key Value. This newly created Key Record is thenadded to the key table of the device. Similarly, the Replace Key is usedto replace the Key Value corresponding to a Key ID with a new value in akey table. The Replace Key function receives as an input the Key ID, andretrieves the Key Record corresponding to the Key ID from the key table.Then, the Key Value in the Key Record is replaced with a new valuegenerated by the PRNG sub-function. For some applications, it may bedesirable to provide a Delete Key function that deletes particular keysfrom a key table of a device. The Delete Key function receives as aninput a particular Key ID in order to delete the corresponding key fromthe key table.

FIG. 11 illustrates the operation of the Export Key function 1100 withreference to Table 1. The Export Key function 1100 is performed by aprovider device 300, 310, 320 in order to export one of its own keys toone or more other devices at specified locations so that the providercan use the key to communicate securely with these other devices. Aslisted in Table 1, the Export Key function 1100 has three inputs,including: (1) Key ID 505; (2) Location ID 140; and (3) Export Key ID1102. These inputs are used by the Export Key function 1100 in order togeo-encrypt the Key Record corresponding to Key ID in the device's keytable. This encryption is done using Location ID 140 and the keyidentified by Export Key ID 1102. As a result, a Cipher Key Record 1112is produced along with a corresponding Cipher Key 526, IV 708, and ShapeParm 509. In a preferred embodiment, the Export Key function 1100 signsthe Cipher Key Record 1112 using a private key 308 owned by the providerthat is stored in the key table of the provider along with other keys.The private key 308 includes the Provider ID in the key ID field andPriv Key Value in the key value field. As a result, a unique Signature1116 is generated for the Cipher Key Record 1112.

The Get Key Record sub-function 1110 will first retrieve the Key Record307 corresponding to the key identified by Key ID 505 from a key table306 of the device. As described previously, the Key Record 307 includesa specific Key ID and a Key value. The Geo-Encrypt function 700 isaccessed to geo-encrypt the retrieved Key Record 307 using the LocationID 140 and Export Key ID 1102. It should be appreciated that in thiscontext the Key Record 307 corresponds to the Plaintext beinggeo-encrypted in the foregoing description with reference to FIG. 7.This results in a Cipher Key Record 1112 that comprises thegeo-encrypted Key Record 307, along with a corresponding Cipher Key 526,IV 708, and Shape Parm 509. The Sign sub-function 1114 is used todigitally sign the Cipher Key Record 1112 using the private key 308stored in the key table of the device, and thereby provide the Signature1116. In a preferred embodiment, the Sign sub-function 1114 usespublic-key cryptography, as noted above.

The Import New Key function 1150 is also shown in FIG. 11 with referenceto Table 1. The Import New Key function 1150 is performed by a providerdevice 300, 310, 320 or receiver device 400 in order to import a keyfrom another device in order to communicate securely with the otherdevice. As listed in Table 1, the Import New Key function 1150 has seveninputs, including: (1) Shape Parm 509; (2) Export Key ID 1102; (3)Cipher Key 526; (4) IV 708; (5) Cipher Key Record 1112; (6) Provider ID1152; and (7) Signature 1116. The Cipher Key Record 1112 is decryptedusing the key identified by Export Key ID 1102 and Shape Parm 509.

More specifically, the Cipher Key Record 1112 is geo-decrypted using theGeo-Decrypt function 720 with Shape Parm 509, Export Key ID 1102, CipherKey 526, IV 708, GPS location signal 727, and Cipher Key Record 1112 asinputs to recover the Key Record 307. A Provider ID Verificationsub-function 1160 will then determine whether the Provider ID 1152corresponds to either the Owner D of the deciphered Key Record 307 or aGeo-encryption Key Authority (GKA) (i.e., an accepted key authority). Ifthe Provider ID 1152 corresponds to one of these, i.e., the Owner D orthe GKA, then the Signature 1116 for the Key Record 307 is validatedusing a Check Signatures sub-function 1170. The Check Signaturessub-function 1170 validates the Signature 1116 for Key Record 307 usingthe public key associated with the Provider ID, which would be obtainedfrom the key table using Provider ID 1152 and possibly other informationto identify the key. If the Signature 1116 proves to be valid, the KeyRecord 307 is added to the key table 406 by sub-function 1166.Conversely, if the Provider ID Verification sub-function 1160 determinesthat the Provider ID 1152 corresponds to neither the Owner ID of thedeciphered Key Record 307 or the GKA, the key table 406 is not updated.It should be noted that the public key associated with Provider D 1152might itself be validated using a certificate stored with the key in thekey table or obtained using any of several methods without altering thescope and spirit of the invention.

The Import New Key function allows administrator devices 310 to add anykey in a key table, including those it does not own. In a preferredembodiment that does not use public-key cryptography for keydistribution, this capability of administrator devices 310 is necessaryfor distributing keys used by new provider devices 300, 320 tocommunicate with receiver devices 400. If the conditions described aboveare met, then the Import New Key function updates the key table toinclude the new Key Record 307. Similarly, the Import Replacement Keyfunction allows administrator devices 310 to change any key in a keytable, including those it does not own. Namely, the Import ReplacementKey function updates the key table by replacing the old Key Recordcorresponding to a particular Key ID with a new one (i.e., the one justimported). The purpose of giving administrator devices 310 thiscapability is so that they can handle a situation where a provider losesits keys or has its keys sabotaged in some way. It may alternatively bedesirable in some circumstances to deny administrator devices 310 thiscapability. The Import Deletion Key function allows administratordevices 310 to delete any key in a key table, including those it doesnot own. The Import Deletion Key function updates the key table bydeleting the Key Record corresponding to a particular Key ID. Thepurpose of giving administrator devices 310 this capability is so thatthey can clear out the keys owned by a defunct provider. It mayalternatively be desirable in some circumstances to deny administratordevices 310 this capability.

In an alternative embodiment of the invention, digital information isassociated with the location identity attribute 140 by encrypting thedigital information using a location-based key. Particularly, a randomdata encrypting key is generated as described above, and a locationvalue is derived from a location identity. The random data encryptingkey and the location value are combined together using an exclusive-ORoperation to provide a location-based key. The location-based key isused to encrypt the digital information. The random data encrypting keyis encrypted using a key encrypting key, and the encrypted random dataencrypting key and the encrypted digital information is communicated tothe receiver. The receiver decrypts the random data encrypting key,determines the location value, and takes the exclusive-OR of the twonumbers together to recover the location key. The digital data can thenbe decrypted using the recovered location key. A drawback of thisalternative approach is that it is not well suited to re-locking orrelay encryption because the digital data is encrypted using locationinformation. Hence, the data itself would have to be re-encrypted, andnot just the key. In applications in which the data is relatively short,then re-encrypting the data may be acceptable.

The functions described above can be used to restrict access to datathat is transmitted over networks and telecommunications systems as wellas data that is stored on a digital medium. As noted earlier, the datacan be of any type and any form. Access to the data may be controlledfor several reasons. For example, the data could be copyright-protected,classified, or sensitive. The following describes exemplary methods forusing these functions to restrict access to transmitted and stored datawhen private-key cryptography is used for key distribution. In thisdescription, it should be appreciated that references are made withrespect to various functions listed in Table 1 along with theircorresponding flow charts provided in FIGS. 7-11. These methods may beused to support a variety of applications. For example, they can be usedto support the secure distribution of movies, television programs,lectures, documents, and other types of data. These methods allow aproducer or distributor of data to limit access to the data. Within thiscontext, receivers may include customers or subscribers. It should beappreciated that different methods may be used if public-keycryptography is used for key management exclusively or in combinationwith private-key cryptography.

In order for a provider to send encrypted data to a receiver, both theprovider device 300, 310, 320 and the receiver device 400 must share acommon secret key encrypting/decrypting key in their respective keytables. This key is owned by the provider, thereby allowing the providerto change it or delete it as desired. It should be noted that the key isnot actually used to encrypt the data. Rather, it is used with locationinformation to encrypt a random data encryption key. Initially, both theprovider devices 300, 310, 320 and the receiver device 400 areinitialized with a secret key that is specific to the administratordevice 310. These keys are loaded into the respective key tables ofprovider devices 300, 310, 320 and receiver device 400 at the time thedevices are produced.

As previously described, the first step is for the administrator device310 to create a key that is owned by the provider and can be used by theprovider to communicate with the receiver. Letting Provider ID denotethe identity of the provider, administrator device 310 first performsthe operation Create Key with input Key ID, where Key ID=(Provider ID,Key Name) for some Key Name. This operation may be performed at therequest of the provider. The effect of the Create Key operation is thata new secret key is created with this Key ID. A record with the key isadded to the key table 316 of the administrator device 310. Next, theadministrator device 310 performs the operation Export Key with inputsKey ID, Provider Location ID, and Provider Export Key ID, where Key IDis the same as before, Provider Location ID is the location of theprovider device 300, 320 and Provider Export Key ID is the identifier ofthe key shared by administrator device 310 and the provider device 300,320. This will yield values Provider Shape Parm, Provider Cipher Key,IV, Provider Cipher Key Record, and Signature, which administratordevice 310 transmits to the provider device 300, 320. Upon receipt, theprovider devices 300, 320 then perform the function Import New Key withinputs Provider Shape Parm, Provider Export Key ID, Provider Cipher Key,IV, Provider Cipher Key Record, and Signature. The purpose of thisfunction is to decrypt Provider Cipher Key Record in order to produce aplaintext Key Record, to validate that the Key Record was signed byadministrator device 310, and then to insert the record into the keytable of the device.

In addition, the administrator device 310 exports the key in a form thatcan be decrypted by the receiver device 400. In particular, theadministrator device 310 performs the function Export Key with inputsKey ID, Receiver Location ID, and Receiver Export Key ID, where Key IDis the same as before, Receiver Location ID is the location of thereceiver device 400, and Receiver Export Key ID is the identifier of akey shared by administrator device 310 and the receiver device 400. Thiswill yield the values Receiver Shape Parm, Receiver Cipher Key, IV,Receiver Cipher Key Record, and Signature, which the administratordevice 310 transmits to the receiver device 400. Upon receipt, thereceiver device 400 then performs the function Import New Key withinputs Receiver Shape Parm, Receiver Export Key ID, Receiver Cipher Key,IV, Receiver Cipher Key Record, and Signature. The purpose of thisfunction is to decrypt Cipher Key Record in order to produce a plaintextKey Record, to validate that the administrator device 310 signed the KeyRecord, and then to insert the record into the device's key table.

If the provider devices 300, 320 request that the secret key be sharedwith multiple receiver devices 400, perhaps even all receiver devices400, then the administrator device 310 exports the secret key to eachsuch receiver device 400 separately using the unique key and location ofeach receiver device 400. Alternatively, the administrator device 310can export the secret key to all receiver devices 400 simultaneously ifthe devices have a common key that is shared with the administratordevice 310. The location used for this would be large enough to includeall the receiver devices 400 that are authorized to receive data fromthis particular provider device 300, 320. It could be, for example, auniversal location that encompasses the entire world. Alternatively, ifa provider device 300, 310 is only authorized to send data to receiverdevices 400 in certain locations, then the administrator device 310could set up the keys in such manner that the provider device 300, 310does not have a shared key with receiver devices 400 outside of theselocations. As new receiver devices 400 join the system, the key can beexported to them accordingly. This approach for establishing a securekey can be used for any pair of entities, for example, a producer device300 and a receiver device 400, or a producer device 300 and adistributor device 320, or a distributor device 320 and a receiverdevice 400, or two distributor devices 320.

Once a provider device 300, 320 has a shared key with a receiver device400 or with multiple receiver devices 400, it can create and export keysof its own to these receiver devices 400 using the same technique usedby the administrator device 310 to create and export keys. For example,a cable-TV company might create a monthly key for paid subscribers usingthe Create Key function. This key would be exported from its deviceusing the Export Key function and sent to paid subscribers. Then, eachmonth the key would be replaced with a new one using the Replace Keyfunction. The new key would be exported with the Export Key function andsent to paid subscribers, who would receive and install it with theImport Replacement Key function. Subscribers who failed to pay would notget the new key, and, therefore, would be unable to decrypt futureprograms.

As another example, a provider device 300, 320 might issue daily keys,identified with key names such as Monday, Tuesday, and so forth. Itwould issue the key for a particular day at the beginning of the day.The daily keys could be exported under longer-term keys such as monthlykeys or individual receiver device 400 keys. Each weekly key would begood for seven days, and would be replaced when that period ends.

As a third example, a provider device 300, 320 might issue keys that areassociated with classification levels. For example, the Key Names mightbe “secret”, “confidential”, and “unclassified”. Secret keys would beissued to receiver devices 400 that are cleared at the “secret” level,“confidential” keys to receiver devices 400 that are cleared at the“confidential” or “secret” level, and “unclassified” keys to allreceiver devices 400 allowed to receive data from the provider device300, 320. Data that is classified “secret” would be enciphered using aLocation Key derived from location and the secret key. “Confidential”and “unclassified” data would be handled in a similar manner.

The administrator device 310 can at any time replace one of its own keysusing the Replace Key function with input Key ID. This function will puta new secret Key Value in its key table record for that Key ID. Theadministrator device 310 then exports the key to provider devices 300,320 and receiver devices 400 using it in the same manner as the originalkey that was exported. At the receiving end, either the provider device300, 320 or receiver device 400 will then use the Import Replacement Keyfunction to import this key.

Once a secret key is established between a producer device 300 and areceiver device 400, the producer device 300 can transmit data to thecustomer at a specific location in such a manner that the data is notaccessible either at other locations or by receiver devices 400 lackingthe key. First, the producer device 300 performs the Geo-Encryptfunction with inputs Location ID, Key ID, and Plaintext, where Plaintextis the digital data, Location ID identifies the location of thecustomer(s), and Key ID identifies the shared key as before. Thisproduces the values Shape Parm, Cipher Key, IV, and Ciphertext, whereCiphertext is the Plaintext encrypted under a random data encrypting keyand Cipher Key is the encryption of the data encrypting key using thelocation specified by Location ID and the key specified by Key ID. Thesevalues are transmitted to one or more receiver devices 400 along withthe Key ID. The intended receiver devices 400 would all share a locationidentified by Location ID.

The receiver devices 400 at the specified location can decrypt the databy performing the Geo-Decrypt function with inputs Shape Parm, Key ID,Cipher Key, IV, and Ciphertext. If the location of the receiver device400 is not correct, or if the receiver device 400 does not have the keyidentified by Key ID, the decryption will fail. If the receiver device400 is implemented with a Geo-Decrypt function that destroys the CipherKey when decryption fails, the Ciphertext will henceforth becomeundecipherable.

A producer device 300 can transmit the same data to multiple receiverdevices 400 at different locations with different secret keys withoutthe need to re-encrypt the data. Instead, it suffices to re-lock the keyunder the different locations and keys. The following shows the methodfor doing this when there are three receiver devices 400. First, theproducer device 300 geo-encrypts the Plaintext for the first receiverdevice 400 using the Geo-Encrypt function with inputs Location ID[1],Key ID[1], and Plaintext. This function produces the results Shape Parm[1], Cipher Key [1], IV, and Ciphertext. These values along with Key ID[1] are transmitted to the first receiver device 400. Next, Cipher Key[1] is re-locked with the location and secret key of the second receiverdevice 400 using the Geo-Relock function with inputs Shape Parm [1], KeyId [1], Cipher Key [1], Location ID [2], and Key ID [2]. This functionproduces the results Shape Parm [2] and Cipher Key [2]. These valuesalong with Key ID [2], IV, and Ciphertext are transmitted to the secondreceiver device 400.

Cipher Key [1] is then also re-locked with the location and secret keyof the third receiver device 400 using the Geo-Relock Key function withinputs Shape Parm [1], Key ID [1], Cipher Key [1], Location ID [3], andKey ID [3]. This function produces the results Shape Parm [3] and CipherKey [3]. These values along with Key ID [3], IV and Ciphertext aretransmitted to the third receiver device 400. Each of the three receiverdevices 400 then uses the Geo-Decrypt function 720 to decrypt the commonCiphertext. It should be appreciated that this method can be extended toany number of receiver devices 400. Furthermore, if there are multiplereceiver devices 400 at a common location and with a common secret key,they can be sent the same values.

A method for securing data distribution from a producer device 300 to areceiver device 400 via a distributor device 320 is similar to thepreceding method except that the producer device 300 does not distributeits data directly to the receiver devices 400. Instead, the data isforwarded to a distributor device 320, which in turn forwards it on toappropriate receiver devices 400. The distributor device 320 re-encryptsthe data (actually, the key) for transmission to these receiver devices400. Initially, the producer device 300 and distributor device 320 sharea secret key that is owned by the producer. In addition, the distributordevice 320 and receiver devices 400 share a key that is owned by thedistributor. Within this embodiment, it should be appreciated that theproducer device 300 does not need to share a key with the receiverdevices 400 or even know the identity of the receivers.

The producer device 300 begins this process by geo-encrypting the datafor transmission to the distributor device 320. This is done byperforming the Geo-Encrypt function with inputs Distributor Location ID,Distributor Key ID, and Plaintext, where Distributor Key ID is theidentifier of the key that is owned by the producer and shared with thedistributor device 320 and Distributor Location ID is the location ofthe distributor device 320. The result of this operation yields thevalues Distributor Shape Parm, Distributor Cipher Key, IV, andCiphertext. The producer device 300 then transmits these values to thedistributor device 320 along with Distributor Key ID. The distributordevice 320 then performs the Geo-Relock Key function with inputsDistributor Shape Parm, Distributor Key ID, Distributor Cipher Key,Receiver Location ID, and Receiver Key ID, where Receiver Key ID is theidentifier of the key that is owned by the distributor and shared withthe receiver device 400 and Receiver Location ID is the location of thereceiver device 400. The result of this operation is a value forReceiver Shape Parm and Receiver Cipher Key. These values aretransmitted to the receiver device 400 along with Receiver Key ID, IV,and Ciphertext. In order to yield Plaintext, the receiver device 400then performs the Geo-Decrypt function with inputs Receiver Shape Parm,Receiver Key ID, Receiver Cipher Key, IV, and Ciphertext. The advantageof this approach is that the producer does not need to know anythingabout the receivers. Moreover, the distributor 320 manages the receiverdevices 400. Such an embodiment could be attractive for a small producer300. For example, a distributor could keep track of sales of theproducer's data to receivers, and then pass along the sales income,minus a service fee, to the producer. Of course, other arrangements arealso possible. For example, the producer could license use of its databy the distributor without regard to individual sales.

With the preceding method, a distributor may readily decrypt and accessplaintext. The distributor could then re-encrypt the data for anyreceiver device 400 to which it has access regardless of the producer'sintentions. With the implementation of a relay encryption function thisis not possible because the producer device 300 locks the dataencryption key first with a location and key that is shared with thereceiver device 400 and then with a location and key that is shared withthe distributor device 320. The distributor device 320 can strip off itsown encryption layer, but not the receiver device's 400 encryptionlayer, so the data can never go to a receiver device 400 other than theone authorized by the producer device 320. With relay encryption, theproducer can also be sure that the data will pass through thedistributor device 320 before it is decrypted, as the receiver device400 cannot remove the encryption layer of the distributor device 320.

In order to achieve this task, the producer device 300 first performsthe Geo-Relay Encrypt function with inputs n, Distributor Location ID,Distributor Key ID, Receiver Location ID, Receiver Key ID, andPlaintext, where it is understood that n=2. This operation yields thevalues Distributor Shape Parm, Receiver Shape Parm, Cipher Key, IV, andCiphertext. These values are transmitted to the distributor device 320along with Distributor Key ID and Receiver Key ID. The distributordevice 320 then uses the key identified by Distributor Key ID to stripoff its layer of key encryption on Cipher Key. This is done byperforming the Geo-Unlock Key function with inputs Distributor ShapeParm, Distributor Key ID, and Cipher Key. This operation yields NewCipher Key, which is transmitted to the receiver device 400 along withReceiver Key ID, Receiver Shape Parm, IV, and Ciphertext. Finally, thereceiver device 400 deciphers the Ciphertext by performing theGeo-Decrypt function with inputs Receiver Shape Parm, Receiver Key ID,New Cipher Key, IV, and Ciphertext. It should be noted that the abovemethod could also be used to relay data through multiple distributordevices 320 instead of just one.

With relay encryption, a producer maintains control over access to itsdata, while still benefiting from the use of a distributor. Such anembodiment could be attractive to large producers. A producer may, forexample, use relay encryption to control the distribution of its datafrom multiple distributors. Within such embodiment, one distributordevice 320 could be given encrypted data destined for receiver devices400 in one geographic region. A second distributor device 320 could thenbe given the same encrypted data, but with the data encryption keyre-locked so as to be decipherable only by receiver devices 400 in asecond region, and so on. Distributors owning the distribution rights ofdifferent geographic regions would thus be unable to infringe upon eachother's regions.

In another embodiment, the Geo-Encrypt 700 and Geo-Decrypt 720 functionsmay be used by any provider device 300, 310, 320 to respectively encryptand decrypt data that is stored by the provider. Within such embodiment,encryption and decryption are specific to the location of the providerdevice 300, 310 and a secret key stored in the provider's key table. Inorder to achieve this task, the provider device 300, 310, 320 firstencrypts the data by performing the Geo-Encrypt function with inputsLocation ID, Key ID, and Plaintext, where Location ID identifies thelocation of the provider device 300, 310, 320 and Key ID identifies thekey of the provider device 300, 310, 320. This produces the values ShapeParm, Cipher Key, IV, and Ciphertext, which would then be stored in theciphertext file along with Key ID. At a later time, the provider device300, 310, 320 decrypts the data by performing the Geo-Decrypt functionwith inputs Shape Parm, Key ID, Cipher Key, IV, and Ciphertext, usingthe values obtained from the ciphertext file.

If the data is to be stored for an extended period, the Cipher Key mightbe relocked with a new key from time to time. Also, if the Key Valueassociated with this particular Key ID ever changes as the result of anUpdate Key operation, Cipher Key would have to be unlocked with the oldvalue and re-locked with a new value before the old value is discarded.Otherwise, the data would become undecipherable.

In summary, by enabling location-based encryption and path-dependentencryption, the present invention has numerous advantages over the priorart. One such advantage is that it adds an additional layer of securityto any encryption system. Not only does the recipient need access to asecret key, but the recipient also must be at a particular location inorder to decrypt data. Another advantage pertains to the distribution ofconfidential materials where one of the parties in the communicationcannot be trusted to maintain the confidentiality of the materials. Thepresent invention uses a combination of location and key table keys,both of which can be implemented transparently to the user, to defeatthe threat of disclosure by a user who cannot be trusted with thecryptographic keys. As previously described, the present invention mayalso be implemented to render digital information unusable if access isattempted that is invalid, by destroying or re-encrypting the digitalinformation.

The present invention enables producers to actively control andparticipate in the encryption of their proprietary data, even afterrelease from their protected domain, through their ability to own andcontrol keys in receiver devices 400 and to multi-lock keys so that datacan only be unlocked by a final receiver 400 and not by intermediatedistributor devices 320. Specifically, digital information can beencrypted in such a way that it can only be decrypted at the receiverdevice 400 if its transmission has followed a pre-defined path over thenetwork 200, passing through specific geographic locations. A uniquemethod is provided by the present invention in which digital informationcan be encrypted in such a way that, as it moves from provider device300, 310, 320 to final receiver device 400, each distributor on the pathto the target location must remove its lock from the cipher key. Finaldecryption is possible only after all locks have been removed.

Key management is often the weakness of a cryptographic system. Thepresent invention addresses this weakness by allowing for the dynamicmanagement of all keys over a network in a secure manner that istransparent to the user and by allowing for the use of public-keycryptography. Also, unlike DRM systems that require separate steps toaccess both the Ciphertext and the key or license required fordecryption, the present invention uses a single digital data acquisitionstep.

Having thus described a preferred embodiment of a system and method fordelivering encrypted information in a communication network usinglocation identity and key tables, it should be apparent to those skilledin the art that certain advantages have been achieved. It should also beappreciated that various modifications, adaptations, and alternativeembodiments thereof may be made within the scope and spirit of thepresent invention. The invention is further defined by the followingclaims.

1. A method for controlling access to digital information, comprising:encrypting said digital information using a data encrypting key;encrypting said data encrypting key using a key encrypting key andinformation derived from a location identity attribute that defines atleast a specific geographic location; and associating said encrypteddata encrypting key with said encrypted digital information such thatsaid encrypted digital information can be accessed only at said specificgeographic location.
 2. The method of claim 1, wherein said locationidentity attribute further comprises at least a location value and aproximity value of said specific geographic location.
 3. The method ofclaim 2, wherein said location value corresponds to a location of anintended receiver of said digital information.
 4. The method of claim 2,wherein said location value further comprises at least one of alatitude, longitude, altitude and time dimension.
 5. The method of claim2, wherein said location value further comprises a universal locationthat encompasses the entire earth.
 6. The method of claim 3, whereinsaid proximity value corresponds to a zone that encompasses saidlocation.
 7. The method of claim 1, further comprising communicatingsaid encrypted digital information to a receiver of said digitalinformation disposed at said specific geographic location.
 8. The methodof claim 1, further comprising identifying location of a receiver atwhich access to said digital information is sought.
 9. The method ofclaim 8, wherein said location identifying step further comprisesrecovering said location from a GPS receiver.
 10. The method of claim 1,wherein said information derived from said location identity attributefurther comprises a location value and a shape parameter.
 11. The methodof claim 1, further comprising: decrypting said data encryption keyusing a key decrypting key and a location value; and decrypting saiddigital information using said data encryption key.
 12. The method ofclaim 11, further comprising deriving said location value from a signalreceived by a GPS receiver and a shape parameter.
 13. The method ofclaim 1, wherein said digital information further comprises a secretkey, and further comprising the step of distributing said secret key toan intended receiver.
 14. The method of claim 11, further comprisingrendering unusable said encrypted digital information if said step ofdecrypting said encrypted digital information is attempted at other thansaid specific geographic location.
 15. The method of claim 11, furthercomprising rendering unusable said encrypted digital information if saidstep of decrypting said encrypted digital information is attemptedwithout using said key decrypting key.
 16. The method of claim 1,further comprising routing said encrypted digital information to anintended receiver through at least one distributor.
 17. The method ofclaim 16, wherein said routing step further comprises adding a layer ofencryption of said data encrypting key for said at least onedistributor.
 18. The method of claim 1, further comprising generatingsaid data encryption key using a pseudo-random number generator.
 19. Themethod of claim 18, wherein said step of generating said encryption keyfurther comprises using GPS signals to partially seed said pseudo-randomnumber generator.
 20. The method of claim 1, further comprisingdecrypting said encrypted data encrypting key, and re-encrypting saiddata encrypting key using at least one of a different location identityattribute and a different key encrypting key.
 21. The method of claim 1,further comprising providing a key table used to store a plurality ofkeys including said key encrypting key.
 22. The method of claim 21,further comprising associating said plurality of keys with respectiveproviders of said digital information.
 23. The method of claim 21,further comprising administering management of said plurality of keys insaid key table.
 24. The method of claim 23, wherein said administeringstep further comprises adding, changing or deleting any one of saidplurality of keys in said key table.
 25. The method of claim 23, whereinsaid key table is located with a remote device, and said administeringstep further comprises adding, changing or deleting any one of saidplurality of keys in said key table remotely.
 26. The method of claim25, wherein said administering step further comprises including asignature when adding, changing or deleting any one of said plurality ofsecret keys in said key table.
 27. The method of claim 21, wherein saidstep of providing a key table further comprises storing keys used forsigning data and validating signatures
 28. An apparatus for controllingaccess to digital information, comprising: a processor having memoryadapted to store software instructions operable to cause said processorto perform the functions of: encrypting said digital information using adata encrypting key; encrypting said data encrypting key using a keyencrypting key and information derived from a location identityattribute that defines at least a specific geographic location; andassociating said encrypted data encrypting key with said encrypteddigital information such that said encrypted digital information can beaccessed only at said specific geographic location.
 29. The apparatus ofclaim 28, wherein said location identity attribute comprises at least alocation value and a proximity value of said specific geographiclocation.
 30. The apparatus of claim 29, wherein said location valuecorresponds to a location of an intended receiver of said digitalinformation.
 31. The apparatus of claim 29, wherein said location valuefurther comprises at least one of a latitude, longitude, altitude andtime dimension.
 32. The apparatus of claim 29, wherein said proximityvalue corresponds to a zone that encompasses said location.
 33. Theapparatus of claim 28, wherein said processor is further operable tocommunicate said encrypted digital information to a receiver of saiddigital information located at said specific geographic location. 34.The apparatus of claim 28, wherein said processor is further operable toidentify location of a receiver at which access to said digitalinformation is sought.
 35. The apparatus of claim 28, further comprisinga GPS receiver coupled to said processor.
 36. The apparatus of claim 28,wherein said information derived from said location identity attributefurther comprises a location value and a shape parameter.
 37. Theapparatus of claim 28, wherein said digital information furthercomprises a secret key, and said processor is further operable todistribute said secret key to an intended receiver located at saidspecific geographic location.
 38. The apparatus of claim 28, whereinsaid processor is further operable to route said encrypted digitalinformation to an intended receiver through at least one distributor.39. The apparatus of claim 28, further comprising a pseudo-random numbergenerator operatively coupled to said processor to generate said dataencrypting key.
 40. The apparatus of claim 28, wherein said processor isfurther operable to decrypt said encrypted data encrypting key, andre-encrypt said data encrypting key using at least one of a differentlocation identity attribute and a different key encrypting key.
 41. Theapparatus of claim 28, wherein said memory further comprises a key tableused to store a plurality of keys including said key encrypting key. 42.The apparatus of claim 41, wherein ones of said plurality of keys areassociated with respective providers of said digital information. 43.The apparatus of claim 41, wherein processor is further operable to add,change or delete any one of said plurality of keys in said key table.44. The method of claim 41, wherein said processor is further operableto provide a signature for authentication of one of said plurality ofkeys.
 45. An apparatus for receiving digital information, comprising: aprocessor having memory adapted to store software instructions operableto cause said processor to perform the functions of: receiving encrypteddigital information and an encrypted data encrypting key; decryptingsaid data encrypting key using a key decrypting key and a locationidentity attribute that defines a specific geographic location of saidapparatus; and decrypting said encrypted digital information using saiddecrypted data encrypting key.
 46. The apparatus of claim 45, whereinsaid function of decrypting said encrypted digital information furthercomprises rendering unusable said encrypted digital information ifdecryption is attempted at other than said specific geographic location.47. The apparatus of claim 45, further comprising a GPS receiver coupledto said processor.
 48. The apparatus of claim 45, wherein said processoris further operable to re-encrypt said data encrypting key using atleast one of a different location identity attribute and a different keyencrypting key.
 49. The apparatus of claim 45, wherein said memoryfurther comprises a key table used to store a plurality of keysincluding said key decrypting key.
 50. The apparatus of claim 45,wherein ones of said plurality of keys are associated with respectiveproviders of said digital information.